Water footprint analysis (hydrologic and economic) of the Guadiana river basin1
M.M. Aldaya
aand M.R. Llamas
ba Twente Water Centre. University of Twente. The Netherlands E-mail: m.m.aldaya@ctw.utwente.nl
bDepartment of Geodynamics. Complutense University of Madrid, Spain E-mail: mrllamas@geo.ucm.es
1 Admitted as an accompanying report to the U.N. World Water Development Report No. 3 to be presented during the 5th World Water Forum (Istanbul, March, 2009)
Table of contents
Summary ... 3
1. Introduction ... 5
2. Study area ... 8
3. Methodology ... 9
4. Data sources and limitations ... 12
5. Results ... 14
5.1 Guadiana water footprint ... 15
A. Crop area ... 15
B. Water consumption ... 16
C. Virtual water content (m3/ton) ... 17
D. Agricultural economic productivity (€/ha) ... 19
E. Economic blue water productivity (€/m3) ... 20
F. Agricultural trade ... 22
5.2 Review of crop water consumption estimates ... 24
6. Conclusions ... 25
Acknowledgements ... 28
Symbols ... 29
Glossary ... 30
Bibliography ... 33
Appendices ... 41
I. Crop area, production and yield ... 41
II. Crop water consumption and virtual water content ... 41
III. Economic value and economic water productivity ... 41
Summary
In most arid and semiarid countries, water resources management is an issue as important as controversial. Today most water resources experts admit that water conflicts are not caused by the physical water scarcity but they are mainly due to poor water management or governance. The virtual water concept, defined as the volume of water used in the production of a commodity, good or service, together with the water footprint (water volume used to produce the goods and services consumed by a person or community), link a large range of sectors and issues, providing an appropriate framework to find potential solutions and contribute to a better management of water resources, particularly in arid or semi-arid countries.
As the most arid country in the European Union, water use and management in Spain is a hot political and social topic. The aim of this study is to analyse the virtual water and water footprint, both from a hydrological and economic perspective, in the semiarid Guadiana basin. The transboundary Guadiana river basin located in south-central Spain and Portugal drains an area of 66,800 km2, of which 17% lies in Portugal. The present analysis is carried out in the Spanish side of the basin which has been divided in Upper, Middle, Lower Guadiana basin and TOP domain. The TOP domain is a group of three small river basins located near the Guadiana River mouth. In these regions the main green and blue water consuming sector is irrigation, with about 95% of total water consumption. Within this sector, high virtual-water low-economic value crops are widespread in the studied Upper and Middle Guadiana regions, particularly cereals with low blue water economic productivity. In particular, the Upper Guadiana basin is among the most significant in Spain in terms of conflicts between agriculture, with almost no food (virtual water) import, and
the conservation of rivers and groundwater-dependent wetlands. On the other hand, in the Lower Guadiana basin and TOP domain, growing vegetables and crops under plastic greenhouses, the blue water economic productivity values are much higher, using jointly surface and groundwater resources. The amount of crops and the employment generated in the whole Guadiana basin is already producing ‘more crops and jobs per drop’. The aim now is to move towards the policy ‘more cash and nature per drop’, especially in the Upper and Middle Guadiana basin.
1. Introduction
In most arid and semiarid countries, water resource management is an issue as important as controversial. Today most water resources experts admit that water conflicts are not caused by the physical water scarcity but they are mainly due to poor water management. The virtual water and water footprint analysis, linking a large range of sectors and issues, provides an appropriate framework to find potential solutions and contribute to a better management of water resources, particularly in water scarce countries.
The water footprint (WF) is a consumption-based indicator of water use defined as the total volume of water that is used to produce the goods and services consumed by an individual or community (Hoekstra and Chapagain, 2008). Closely linked to the concept of water footprint is the virtual water. The virtual water content of a product (a commodity, good or service) refers to the volume of water used in its production (Allan, 1997; 1999;
Hoekstra, 2003). Building on this concept, virtual water ‘trade’ represents the amount of water embedded in traded products (Hoekstra and Hung, 2002). A nation can preserve its domestic water resources by importing water intensive products instead of producing them domestically (ibid.). These ‘water savings’ can be used to produce alternative, higher-value agricultural crops, to support environmental services, or to serve growing domestic needs.
Thus, virtual water ‘import’ is increasingly perceived as an alternative source of water for some water-stressed nations and is starting to change the current concepts of water and food security.
Furthermore, the virtual water and water footprint analysis makes explicit how much water is needed to produce different goods and services. In semi-arid and arid areas, knowing the virtual water value of a good or service can be useful towards determining how best to use the scarce water available. In this sense, it is important to establish whether
the water used proceeds from rainwater evaporated during the production process (green water) or surface water and/or groundwater evaporated as a result of the production of the product (blue water) (Chapagain et al., 2006; Falkenmark, 2003). Traditionally, emphasis has been given to the concept of blue water through the ‘miracle’ of irrigation systems.
However, an increasing number of authors highlight the importance of green water (Allan, 2006; Comprehensive Assessment of Water Management in Agriculture, 2007; Falkenmark and Rockström, 2004; Rockström, 2001). Virtual water and water footprint assessment could thus inform production and trade decisions, promoting the production of goods most suited to local environmental conditions and the development and adoption of water efficient technology. Adopting this approach, however, requires a good understanding of the impacts of such policies on socio-cultural, economic and environmental conditions.
Besides, water is not the only factor of production and other factors, such as energy, may come to play an increasingly important role in determining water resources allocation and use.
The present study deals with the economic and hydrological analysis of the virtual water and water footprint of the Guadiana river basin, considering both green and blue (ground and surface) water of the different economic sectors. This could facilitate a more efficient allocation and use of water resources, providing simultaneously a transparent interdisciplinary framework for policy formulation. The Guadiana river basin is shared by Spain and Portugal, but this report focuses on the Spanish area of the river basin. The analysis of the Portuguese area (less than 20% of the total area of the basin) will be carried out by the Portuguese INAG (National Water Authority). It analyses the water footprint, virtual water and economic relevance of each economic sector in different rainfall years (evaluating an average - 2001, dry -2005, and humid year -1997). Special emphasis is given
to the agricultural sector, which consumes about 95% of total green and blue water resources. First of all, the whole Guadiana is evaluated, which has been divided in four sections: groundwater based Upper Guadiana basin, mainly surface water based Middle basin, both groundwater and surface water based Lower Guadiana basin and the former Lower Guadiana or Guadiana II (henceforth TOP domain)2 comprising the Tinto, Odiel and Piedras river basins. At the end of the chapter virtual water ‘trade’ is evaluated. Finally, crop water consumption estimates are assessed against the results obtained by other national and international studies. A glossary with key terms is also included at the end of the study, a more extensive version can be found in (Aldaya and Llamas, in press). It concludes that a better knowledge of the water footprint and virtual water ‘trade’ in the semiarid Guadiana basin provides a transparent and multidisciplinary framework for informing and optimising water policy decisions, contributing at the same time to the implementation of the EU Water Framework Directive (2000/60/EC). As a whole, the Guadiana river basin has already achieved a good degree of the paradigm ‘more crops and jobs per drop’ but it is still far from achieving ‘more cash and nature per drop’. An exception for this is the case of the Lower Guadiana basin and TOP domain in Andalusia, where virtual water-extensive high economic value crops adapted to the Mediterranean climate are grown, essentially vegetables, fruits and olive oil. For the time being and almost in the entire world, water footprint analysis has focused on hydrological aspects. A significant innovation of this work is to emphasize the imperative challenge of considering economic and ecological aspects, with the aim of going towards the new paradigm ‘more cash and nature per drop’ (Aldaya et al., 2008). Finally, the water footprint analysis is
2 Before 1 January 2006 the TOP domain was the competence of the Guadiana River Basin Authority, after this date it was transferred to the Government of Andalusia.
providing new data and perspectives that are enabling to get a more optimistic outlook of the frequently spread looming «water scarcity crisis». We expect that this new knowledge makes traditional water and food security concepts change, concepts that have hitherto prevailed in the minds of most policy makers.
2. Study area
The Guadiana basin has an area of about 67,000 km2 (83% in Spain and 17% in Portugal).
The climate is semiarid, with an average precipitation of about 450 mm/year and average annual temperature of 14-16 ºC (CHG, 2008a; INAG, 2007).
For practical purposes, the basin has been divided in four areas (Figure 1): a) groundwater based Upper Guadiana basin (totally located in a part of the Castilla-La Mancha Autonomous region); b) mainly surface water based Middle Guadiana basin (comprising part of Extremadura but not the small fraction of Cordoba); c) the Lower Guadiana basin (including the part of the basin in Huelva); and d) TOP domain (comprising the Tinto, Odiel and Piedras river basins). The TOP domain was the competence of the Guadiana River Basin Authority before 1 January 2006, but its competence was then transferred to the Government of Andalusia (CHG, 2008a).
Figure 1. Guadiana river basin geographic and administrative domain from 1 January 2006
onwards (CHG, 2008a)
According to CHG (2008b) when referring to the Guadiana river basin on the whole (‘Total Guadiana’ in the present document), it includes the Upper, Middle and Lower basins including the small fraction of Cordoba.
Figure 2. Western Mancha aquifer location within the Upper Guadiana Basin. Modified from CHG (2008b).
The Upper Guadiana basin, located in Castilla-La Mancha, is one of the driest river basins in Spain (Hernández-Mora et al., 2003). In this part, UNESCO recognized the collective ecological importance of 25,000 ha of wetlands in 1980, when it designated the ‘Mancha Húmeda’ Biosphere Reserve. In a largely arid region, these wetlands provided crucial nesting and feeding grounds for European migrating bird populations and were home to rare animal and plant species. The Tablas de Daimiel National Park (2,000 ha), a Ramsar Site, stands out for its significance as a symbol for the Spanish conservation movement.
Today, however, this wetland that used to receive the natural discharge from the Western Mancha aquifer (Figure 2), survive artificially, in a kind of ‘ecological coma’, thanks to the water transfers that come from the Tagus-Segura Aqueduct starting in 1988 (Hernández- Mora et al., 2003) and to the artificial pumpage of groundwater to maintain flooded about the 5% of the 2,000 hectares of wetlands in the undisturbed National Park. More recently, some NGOs are claiming that ‘La Mancha Humeda, Biophere Reserve’ should not be considered any more by UNESCO as a World Biosphere Reserve. On the other hand, in order to recover these ecosystems, the Spanish Government, at the proposal of the Ministry of the Environment, approved a Special Plan for the Upper Guadiana (Plan Especial del Alto Guadiana –PEAG) on 11 January 2008 (CHG, 2008c). The formal approval of this Plan includes a budget of 5,500 million euros to be spent during the next 20 years.
3. Methodology
The present study estimates the virtual water and water footprint of the Guadiana river basin considering the green and blue water components for the most representative crops and the blue water component for livestock, industrial products and domestic (urban) water use. Within the blue water component, the volumes of surface and groundwater consumption are differentiated. In parallel with these analyses, economic data are studied.
This is done for each section of the river basin (Upper, Middle, Lower Guadiana and TOP domain) at different time scales (for an average -2001, dry -2005, and humid year -1997).
The virtual water and water footprint are calculated using the methodology developed by Hoekstra and Hung (2002; 2005) and Chapagain and Hoekstra (2003; 2004). For its emphasis on green and blue water, the present research follows recent works of Chapagain et al. (2006) Hoekstra and Chapagain (2008) and Chapagain and Orr (2008).
The method followed in this work is described in more detail in a more extensive report of the Guadiana river basin (Aldaya and Llamas, in press).
Virtual water content
The virtual water content of a product is the volume of freshwater used to produce the product, which depends on the water use in the various steps of the production chain. The virtual water content of primary crops (m3/ton) (i.e. crops in the form as they come directly from the land without having undergone any processing) has been calculated at a provincial level as the ratio of the volume of water used during the entire period of crop growth (crop water use, m3/year) to the corresponding crop yield (ton/ha) in the producing region. The crop water requirement of a certain crop under particular climatic circumstances was estimated with the CROPWAT model (Allen et al., 1998; FAO, 2003) using climate data at a provincial level. The volume of water used to grow crops in the field has two components: effective rainfall (green water) and irrigation water (blue water).
One particularity of the methodology used in this detailed study is that rainfed and irrigated agriculture were differentiated in the green and blue virtual water component calculations. That is, the green component in the virtual water content of a primary crop (Vg, m3/ton) is calculated as the green crop water use (m3/ha) divided by the crop yield (Y, ton/ha) for both rainfed (Yr) and irrigated production (Yirr). In parallel, the blue water
component (Vb, m3/ton) is calculated as blue crop water use divided by crop yield in irrigated production (Yirr).
Water footprint
In line with Chapagain and Hoekstra (2004), the water footprint of a country is equal to the total volume of water used, directly or indirectly, to produce the goods and services consumed by the inhabitants of the country. A national water footprint has two components, the internal and the external water footprint. First, the internal water footprint is defined as the volume of water used from domestic water resources to produce the goods and services consumed by the inhabitants of the region (Hoekstra and Chapagain, 2008). It is the sum of the total water volume used from the domestic water resources in the national economy minus the volume of virtual water export to other countries insofar related to export of domestically produced products. Second, the external water footprint is the volume of water used in other regions to produce goods and services imported and consumed by the inhabitants of that region. The present study calculates the water footprint per sub-basin related to production. Trade data at a provincial level are presented separately.
4. Data sources and limitations
In order to carry out this report, a number of simplifications have been assumed. First of all, the virtual water content values obtained with the CROPWAT model should be considered as a first approximation to reality. The main gaps in this approach are: a) the lack of data on the soils characteristics and their storage capacity for the effective rain; b) the amount of irrigation water ‘lost’ from the surface reservoirs to the field; c) the amount of water necessary to abate the pollution; and d) the reduction in crop yield when the irrigation demand cannot be supplied. Second, the eight most representative crops in each area have been studied corresponding to about 80% of the total area (Appendix 1). Third, with the aim of analysing the impact of climate variability on the use of water resources three different rainfall years were chosen: a humid (1997), average (2001) and dry year (2005).
The average rainfall in 2001 was about 355 mm in Castilla-La Mancha, 547 in Extremadura and and 510 mm in Andalucía. When available, data for these years were used. This was not possible, however, in every case as shown below in this chapter. Fourth, and following CHG (2008b) data, when estimating the urban water use, urban water supply and sanitation data have been taken into account. Fifth, concerning the industrial water use, since energy and building industry are not considered within the industrial sector, hydroelectric energy was not included (CHG, 2008b). Sixth, with regard to the livestock water consumption, the drinking water and water to clean its housing is considered, leaving out the water used to grow and process its fodder. This is important when comparing these data with other analyses of the livestock water footprint. Finally, data have been compiled from different sources.
Geographic and social data: Data related to human population and employment were taken from the Guadiana River Basin Authority (CHG, 2008b).
Climatic data: Average monthly rainfall and evapotranspiration data at provincial level, as an input for the CROPWAT model (FAO, 2003), were obtained from the National Institute of Meteorology (INM, 2007).
Agricultural data: Data related to area (total area, crop area both rainfed and irrigated, irrigated area by irrigation system) were taken from the Guadiana River Basin Authority (CHG, 2008b) and the Spanish Ministry of Agriculture, Fisheries and Food 1T sheets (MAPA, 1999; 2001b).
Data on average rainfed and irrigated crop yield (Y) (kg/ha) at provincial level were taken from the Agro-alimentary Statistics Yearbook of the Spanish Ministry of Agriculture, Fisheries and Food (MAPA, 2007).
With regard to the crop parameters, as input data to CROPWAT, the crop coefficients in different crop development stages (initial, middle and late stage) were taken from FAO (Allen et al., 1998; FAO, 2003). The length of each crop in each development stage was obtained from FAO (Allen et al., 1998; FAO, 2003) when the climate region was specified;
otherwise it was obtained from the work of Chapagain and Hoekstra (2004). The crop calendar was taken from the Spanish Ministry of Agriculture, Fisheries and Food (MAPA, 2001a). These data are also given at provincial level.
Economic data: Data related to gross value added (GVA) were taken from the Guadiana River Basin Authority (CHG, 2008b). Gross Value Added is obtained by deducting intermediate consumption from final agricultural production. That is, the gross value added is equal to net output or benefit to the farmer that can be used for the remuneration of productive factors. Nevertheless, in this study we will focus on the final economic agricultural production (total €) as well.
Crop economic value (€/ton) for the different years was obtained from the Spanish Ministry of Agriculture, Fisheries and Food (MAPA, 2007). We are aware, however, that prices may change significantly from one year to the other. These data are an average for the whole Spain. In the present report CAP subsidies were not included (CHG, 2008b).
Hydrologic data: Data related to water origin (surface and groundwater) by agricultural region were taken from the Guadiana River Basin Authority (CHG, 2008b), which is based on the 1999 Agrarian Census of the National Statistics Institute (INE, 2007).
Green and blue crop consumptive water use (CWU, m3/ha) data were estimated using the CROPWAT model (FAO, 2003) (see Methodology section). Data on blue water withdrawals (surface and ground water) were taken from the Guadiana River Basin Authority (2007). It is noteworthy that these withdrawals are not the same as the estimated water consumption or evapotranspirative demand.
Average global irrigation efficiency at provincial level was taken from the CHG (2008b).
It depends on the type of irrigation technique used by the farmer. Localized or drip irrigation is the most efficient system with a 0.9 coefficient, followed by sprinkler irrigation with 0.7 and finally, surface flood irrigation with 0.5.
Trade data: Data related to international trade at a provincial level were taken from ICEX (2008).
5. Results
Since irrigated agriculture is the main blue water user in the Guadiana Basin (about 90%
according to MIMAM, 2007), the present study mainly focuses on water use by this sector.
First of all, as seen in the methodology chapter, the Guadiana river basin has been divided and analyzed in four areas (Upper, Middle, Lower Guadiana and TOP domain). Then, the
obtained green and blue crop water consumption values are compared with national and international studies.
5.1. Guadiana water footprint
When comparing the Guadiana basin Gross Value Added (GVA) with national figures for the different sectors, the agricultural sector represents a value of 8.4 % of the national total, having both agriculture and livestock similar shares. Agriculture of the TOP domain represents 1.6 % of the national GVA, representing the livestock just a small amount (0.3
%). Concerning the manufacture industrial sector GVA, both in the Guadiana basin and TOP domain, it is not relevant in comparison with the total national, representing 1.99 % and 0.45 % of the total national respectively. These figures show the relevance of agriculture in these areas in comparison with other Spanish regions where industry and tourism are more important.
A. Crop area
The Spanish Guadiana river basin crop area is 26,000 km2, which is about 47% of the total area. As a whole, in the basin, 19% of the crop area is devoted to irrigated agriculture. This proportion is similar to the Spanish average which amounts to 22% (MIMAM, 2007).
As shown in figure 3, the area dedicated to each crop type varies in each Guadiana section in the year 2001 (average precipitation). When looking at the rainfed agriculture similar crops are grown in the different Guadiana sections, highlighting cereals, olive trees and vineyards. Concerning irrigated agriculture, in general, cereals, vineyards and olive trees dominate in the Upper and Middle Guadiana basins, whereas citrus trees and vegetables in the Lower Guadiana and TOP domain. After the Common Agricultural Policy reform (2003), however, vineyard and olive tree irrigated production has increased significantly in Spain (18% y 16% respectively) (MAPA, 2006). According to Garrido and Varela (2008)
this is notable in Castilla- La Mancha Autonomous Community. It is expected that significant changes in crop distribution will continue to occur in the near future due to different causes, such as the increase in cereal prices.
Figure 3. Percentage of areas of irrigated and rainfed crops in the Upper, Middle, Lower Guadiana
and TOP domain (average-year 2001). Showing crops occupying over 1% of land. Source: CHG (2008b).
B. Water use and consumption: total and by the agricultural sector Total Water Use
As in most arid and semiarid regions, in the Guadiana river basin the main green and blue water consuming sector is irrigation, with about 95% of total water consumption in the basin as a whole (Table 1). The following main blue water user is urban water supply with less than 5% of the water applied for irrigation. If we consider that most urban water returns to the system, it can be said that irrigation consumptive uses are more than 95% of all the uses. However, the security of this supply is extremely relevant from a political and economic point of view. Concerning the Andalusian part (Lower Guadiana and the so- called TOP domain), irrigation consumes a lower water proportion, of about 75-80%, which account for the increase of the urban water supply. The industrial sector, even if it is the smallest water user, represents the highest economic value (GVA). Agriculture is also a significant economic activity in the Guadiana river basin, being the most important share of the GVA after the industrial sector (Table 1). Thus, even if urban and industrial uses have an obvious economic and social relevance, agriculture, as the highest water consumer in the basin, is the key to water resources management in the area.
Concerning rainfed and irrigated farming in the whole basin excluding TOP domain, total rainfed area is more than five times the irrigated area (2,100x103 and 400x103 hectares
respectively) (Appendix 2). Rainfed systems consume about 55% of the total water consumed by the agricultural sector (Table 1) and use green water (i.e. rainfall) that has a lower opportunity cost compared to the blue water use (i.e. irrigation) (Chapagain et al., 2005). Even if significantly smaller in extension, irrigated agriculture produces more tonnes and euros than rainfed agriculture (Appendix 2A and 2C).
Table 1. Internal water footprint of the Guadiana basin (year 2001) Agricultural water consumption
As shown in figure 4, when taking into account rainfed and irrigated water consumption, crop water requirements are somewhat higher in the humid year. As it might be expected, there are remarkable variations in the green and blue water proportions in years with different rainfall patterns, being the blue water consumption higher in dry years and lower in humid years. While logically the green water consumption shows the opposite pattern.
Figure 4. Theoretical green and blue agricultural water consumption (Mm3/year) in the Upper, Middle, Lower Guadiana and TOP domain a dry (2005), average (2001) and humid year (1997). Source: Own elaboration.
The blue water consumption in the Upper Guadiana basin is mainly based on its groundwater resources, whereas the Middle Guadiana basin uses its surface water resources, mainly coming from large surface water reservoirs (Figure 5). The Lower Guadiana basin and TOP domain combine both ground and surface water strategies.
Figure 5. Theoretical green and blue (surface and ground) agricultural water consumption (Mm3/year) in the Upper, Middle, Lower Guadiana and TOP domain a dry (2005), average (2001) and humid year (1997). The size of the circle is proportional to the volume of water.
Source: Own elaboration.
C. Virtual water content in irrigated lands (m3/ton)
The virtual water analysis establishes the amount of water required by specific crops and it differs considerably among crop and climate types. For instance, Spain has a comparative advantage over most of the other European countries in the production of Mediterranean crops (such as vegetables, citrus fruits, vineyards or olive oil). It is also important to determine whether the water used proceeds from blue (i.e. irrigation) or green water (i.e.
rainfall), and whether the blue water is surface or ground water.
Figure 6 provides an overview of the virtual water content of irrigated crops (m3/ton) in the different sections of the Guadiana basin in the different rainfall years. As shown in this figure, it is noteworthy that, among the studied crops, industrial crops (such as sunflowers), grain legumes, grain cereals (1,000-1,300 m3/ton) and olive trees (about 1,000-1,500 m3/ton) show the highest virtual water contents in irrigated agriculture. In humid years, however, olive trees are mainly based on green water resources. As previously mentioned, until recently, olive trees (and vineyards) were typical rain-fed crops. However, in last years the irrigated area seems to be significantly increasing for both crops.
It is widely believed that maize and vegetables are water-wasteful since in terms of m3/ha these crops consume large amounts of water. Nevertheless, when looking at the virtual water content in m3/kg these crops consume less water than it is generally believed. In fact, among the studied crops vegetables (100-200 m3/ton) exhibit the smallest virtual water content figures, probably due to the high yields they have.
Finally, vineyards have intermediate virtual water contents, of about 300-600 m3/ton.
Despite the semiarid nature of the Guadiana basin, in the Upper and Middle Guadiana basin irrigated grain cereal production is widespread in the year 2001. Aside from cereals, vineyards and olive trees are the most widespread crop in the basin during the year 2001.
Two reasons may explain this trend. First, vineyards are significantly water-efficient (in
fact, vineyards are traditionally considered dryland crops) and second, irrigated vineyards provide quite high economic revenue per hectare.
In the Lower Guadiana basin and TOP domain, on the other hand, irrigated citrus trees and vegetables account for most part of the irrigated area and represent the highest total economic values in this region. What occurs in these two small areas of our study is a general situation in other coastal areas of Andalusia (Hernández-Mora et al. 2001; Vives, 2003).
The economic value of agricultural commodities is an important aspect. For example, many farmers have moved from water-intensive and low economic value crops to water- extensive and higher economic value crops. Alfalfa has been substituted by grapevine or olive trees (Llamas, 2005). According to Llamas (2005) the motto ‘more crops and jobs per drop’ should be replaced by ‘more cash and nature per drop’. Nevertheless, there is still a long way to go to achieve this motto in the Upper and Middle Guadiana basins. In the Lower Guadiana and TOP domain it has been partly achieved, at least on its first half.
Figure 6. Irrigated agriculture green and blue virtual content per crop and year in the different Guadiana sections: UG: Upper Guadiana, MG: Middle Guadiana, LG: Lower Guadiana and TOP domain in different rainfall years (m3/ton). Source: Own elaboration.
D. Agricultural economic productivity (€/ha)
As it is widely known, agricultural economic productivity of irrigated agriculture is higher than that of rainfed agriculture (Berbel, 2007; Hernández-Mora et al., 2001; MIMAM, 2007). In the case of the Guadiana basin this is true for any type of year (average, humid and dry) (Figure 7). From a socio-economic perspective, irrigated agriculture not only provides a higher income, but also a safer income. This is due both, to the higher
diversification it allows, and to the reduction of climate risks derived from rainfall variability (Comprehensive Assessment of Water Management in Agriculture, 2007).
Concerning the agricultural economic productivity per crop of irrigated agriculture, vegetables have the highest revenues per hectare (5,000-50,000 €/ha). Followed by vineyards (about 4,000-6,000 €/ha), citrus in the Andalusian section (3,000-5,000 €/ha), potatoes (2,000-6,000 €/ha) and olive trees (about 1,000-3,000 €/ha). Finally grain cereals, grain legumes and industrial crops have productivities of less than 1,000 €/ha.
Figure 7. Economic productivity of irrigated and rainfed agriculture per hectare by crop type in the
different Guadiana sections in different rainfall years (€/ha). Source: Own elaboration.
E. Economic blue water productivity (€/m3)
The agricultural total water economic productivity has been calculated in two different ways: using GVA (CHG, 2008b) (Table 1) and using crop economic value (MAPA, 2002) (Figure 8). In both cases the highest value per cubic meter is obtained in the Andalusian part (including the Lower Guadiana and TOP domain), due to the high economic value of the vegetables, which are widespread in the region.
According to Llamas and Martínez-Santos (2005), most probably high value crops are watered with groundwater resources or combining ground and surface water. For instance, Hernández-Mora et al. (2001) show that, in Andalusia (in a study considering almost one million irrigated hectares), agriculture using groundwater is economically over five times more productive and generates almost three times the employment than agriculture using surface water, per unit volume of water used. This difference can be attributed to several causes: the greater control and supply guarantee that groundwater provides, which in turn allows farmers to introduce more efficient irrigation techniques and more profitable crops;
the greater dynamism that has characterized the farmer that has sought out his own sources
of water and bears the full costs of drilling, pumping and distribution; and the fact that the higher financial costs farmers bear motivates them to look for more profitable crops that will allow them to maximize their return on investments (Hernández-Mora et al., 2001).
Surface and groundwater distinction, therefore, should be taken into account in order to achieve an efficient allocation of water resources. Furthermore, in line with previous studies in arid and semi-arid regions (Garrido et al., 2006; Hernández Mora et al. 2001;
Vives 2003), the social (jobs/m3) and economic (€/m3) value of groundwater irrigation generally exceeds that of surface water irrigation systems. Agricultural water economic productivity was thus expected to be higher in groundwater based areas.
Along these lines, the Lower Guadiana basin and TOP domain, with a joint surface and groundwater use, have the highest agricultural water economic productivities because they predominantly grow cash crops. The groundwater based Upper Guadiana basin has intermediate values, whereas the surface water based Middle Guadiana shows the lowest water economic productivities. Nevertheless, Upper and Middle Guadiana present similar values in dry years. Probably, this small difference is due on the one hand, to the water irrigation security provided by the existing large surface water reservoirs in the Middle Guadiana; and, on the other, because the use of groundwater in the Upper Guadiana basin has serious legal and political restrictions, at least in theory.
Figure 8. Total blue water economic productivity (€/m3) concerning agricultural water consumption by year in the Upper, Middle and Lower Guadiana and TOP domain. Source: Own elaboration.
The water economic productivity analysis can be very useful in order to identify possible water uses not justified in economic efficiency terms and achieve an efficient allocation of water resources.
According to MIMAM (2007), average productivity of blue water used in irrigated agriculture in Spain is about 0.44 €/m3. When looking at the productivity per crop type in the Guadiana basin (Figure 9), vegetables (including horticultural and greenhouse crops) present the highest economic value per water unit (amounting to 15 €/m3 in the Andalusian part: Lower Guadiana and TOP domain). These numbers are similar to the figures estimated by Vives (2003) for greenhouse cultivation using groundwater in Almeria, which amount to 12 €/m3. With lower values vineyards (1-3 €/m3), potatoes (0.5-1.5 €/m3), olive tree (0.5-1 €/m3) and citrus trees (0.3-0.9 €/m3) show intermediate values. Finally, with remarkably lower values, grain cereals, grain legumes and industrial crops display an average productivity of less than 0.3 €/m3. These data clearly show that the problem in the Guadiana basin is not water scarcity but the use of water for low value crops. Once again, the policy in the near future has to be to more cash per drop.
Figure 9. Blue water economic productivity (€/m3) concerning agricultural water consumption by crop and year in the Upper, Middle and Lower Guadiana and TOP domain. Source: Own elaboration.
F. Agricultural trade
The international trade data provided in this section are given at a provincial level as more disaggregated data were not found (ICEX, 2008). The main provinces of each river basin section have been analysed: Ciudad Real for the Upper Guadiana, Badajoz for the Middle Guadiana and Huelva for the Lower Guadiana and TOP domain. Part of the data concerning Ciudad Real and Badajoz were already considered in section 7.1 F.
Concerning trade in tonnes, euros and virtual water, it is noteworthy that Ciudad Real is a net exporter, mainly of wine, and barely imports any commodity (Figure 10). During the
studied period this province has relied on its own food production without depending on global markets. This has been probably at the cost of using its scarce water resources.
In relation to Badajoz, is a net canned-tomato exporter, while importing other commodities such as cereals. It has to be highlighted the increase in cereal imports in drier years (Figure 11).
Huelva also imports virtual water intense commodities, such as cereals, whereas exports low virtual water content fruits (Figure 12). The drier the year the higher the cereal imports.
In hydrologic terms, cereal virtual water imports save 1015 Mm3 in Huelva, whereas vegetable exports just uses 100 Mm3. Even if in terms of tonnes and water consumption cereal imports remarkably surpass fruit exports, in economic terms fruit exports are much more important than cereal imports. These results are in line with those obtained by Chahed et al. (2007) when analysing the water footprint in Tunisia, even if they did not assess the economic aspects.
Virtual water imports, and in particular cereal imports, play a role in compensating for the water deficit and providing water and food security in the Middle Guadiana and Andalusian part (Lower Guadiana and TOP domain). For these regions, however, the underlying motivation of importing food (virtual water) is probably hardly a pursuit of comparative advantage, but to fill the domestic shortfall of food supply and to maintain social stability.
According to the World Water Council (2004) one can only speak of virtual water ‘trade’
if conscious choices are made in water and environmental management policies whether or not to make water available or to release pressure on the domestic water resources by importing goods that else would have consumed much of the domestic water resources available. To make conscious choices, the elements of choice and the players involved in virtual water ‘trade’ have to be made visible. Allan (2001) states that virtual water ‘trade’ is
so successful because it is invisible and is applied beyond the general political debate.
However, invisibility may lead to postponement of necessary reforms by politicians as imports can be regarded as ‘secret reserves’ that might bail out in the short run (Warner, 2003).
Finally, the concept of virtual water ‘trade’ could be very relevant for this region. Local planning and regional collaboration incorporating the notion of virtual water ‘trade’ could result in exchange of goods, diversification of crops, diet awareness creation or crop replacement actions.
Figure 10. Agricultural commodity export and import in thousand tonnes, million euros and million
cubic metres from Ciudad Real during the years 1997 (Humid), 2001 (average) and 2005 (dry).
Source: Own elaboration based on ICEX (2008) and Chapagain and Hoekstra (2004) data.
Figure 11. Agricultural commodity export and import in thousand tonnes, million euros and million
cubic metres from Badajoz during the years 1997 (Humid), 2001 (average) and 2005 (dry). Source:
Own elaboration based on ICEX (2008) and Chapagain and Hoekstra (2004) data.
Figure 12. Agricultural commodity export and import in thousand tonnes, million euros and million
cubic metres from Huelva during the years 1997 (Humid), 2001 (average) and 2005 (dry). Source:
Own elaboration based on ICEX (2008) and Chapagain and Hoekstra (2004) data.
5.3. Review of crop water consumption estimates by various experts
The present study should be taken as a very interesting but rough approximation to the reality. In tables 2 and 3 green and blue water requirements of the analysed crops by various sources are presented.
When comparing the green water consumption data with other sources, there is a remarkable disparity derived from the methodology in use (Table 2). The present green crop water use numbers, based on FAO Penman-Monteith equation and CROPWAT model,
are higher than figures given by the ITAP (2008), based on the FAO Penman-Monteith equation and an estimation of effective irrigation as 70% of total rainfall. Furthermore, small changes in planting and harvest dates entail big changes in crop water use figures (m3/ha). This could explain these differences.
With regard to the different rainfall years, as expected, there are notable differences depending on the type of year, being lower in dry years (Table 2).
When looking at the theoretical blue water consumption values, the present research results do not seem to differ significantly from other sources (Table 3). As shown in table 2, wheat and other cereals as a whole consume great amounts of blue water whereas their economic value in the markets is very low. Olive tree and vineyard blue water requirements vary depending on the source but they are generally somewhat lower than those of the cereals.
In our opinion, even if these data are a first approximation, they clearly show that the water policy in the Guadiana Basin can and should apply progressively the motto ‘more cash and nature per drop’.
6. Conclusions
1. The present virtual water and water footprint analysis, both hydrological and economic, of the Guadiana river basin, provides very interesting results. This analysis however is a first approximation. The calculated theoretical crop water requirements somewhat differ from other authors. There is an outstanding dispersion of data amounting to 100% in certain cases that may be originated by the different methodologies. On the whole, our crop water requirements are based on FAO Penman-Monteith equation and CROPWAT model, whereas figures given by the CHG (2008b) and SIAR (2008) are based on the Thornthwaite and FAO Penman-Monteith equation respectively. In other cases, the uncertainties on some
basic data are related to political issues. One example of this is the lack of acceptable accuracy on the inventory of water users and rights, and on the irrigated area by legal and illegal water wells.
2. As in most arid and semiarid regions, in the Guadiana river basin the main green and blue water consuming sector is irrigation, with about 95% of total water consumption in the basin as a whole. Concerning the blue water economic productivity, however, urban water supply and industry values are higher than the corresponding value in agriculture. The multifunctional value of agriculture, however, has to be taken into account. Rainfed agriculture has a high relevance in the Guadiana basin in terms of total hectares.
Agricultural economic productivity (ton/ha) and total production (ton/year) of rainfed agriculture, however, are notably lower than that of irrigated agriculture. Thus, even if less in extension, irrigated agriculture produces more tonnes and euros than rainfed agriculture.
This economic and social fact explains the political relevance of groundwater irrigation in the Upper Guadiana basin.
3. As a whole, high virtual-water low-economic value crops are widespread in the analysed Upper and Middle Guadiana regions. For instance, cereals exhibit virtual water values of 1,000-1,300 m3/ton or even higher in dry years. On the other hand, maize and vegetables (mainly tomato and melons) present the smallest values with around 600 and 100-200 m3/ton respectively, due to their high yields.
4. One of the most important contributions of the present report is the analysis of the economic productivity of blue water use for the different crops. In the Upper and Middle Guadiana basin, it seems to range between 0.1-0.2 €/m3 for low cost cereals and 1.5-4.5
€/m3 for vegetables. These values are relatively small in comparison with the ones obtained in the Andalusian region (Lower Guadiana and TOP domain). In this region, for vegetables
(including horticultural and crops under plastic) using jointly surface and groundwater resources, this value can amount to 15 €/m3. Even with lower figures, vineyards (1-3 €/m3) and olive trees (0.5-1 €/m3) seem to be profitable crops. As a matter of fact it is widely known that farmers are currently changing their production to vineyards and olive trees. It could be interesting to examine these trends in the near future.
5. Nevertheless, we can not fall into the simplification that all the water that is not used for vegetables or trees is wasted water. Factors such as risk diversification, labour or other environmental, social, economic and agronomic reasons have to be taken into account in order to find a balance. The major environmental challenge of agriculture is the preservation of the environment without damaging the agricultural sector economy. The amount of crops and the employment generated in the whole Guadiana basin is producing
‘more crops and jobs per drop’. The aim now is to achieve the paradigm ‘more cash and nature per drop’. The present results, indicating the low water consumption and high economic value of vegetables, followed by vineyards, is one of the factors that has to be taken into account in order to achieve an efficient allocation of water and economic resources.
6. Finally, a first estimation of trade in agricultural products is provided considering the international import-exports at a provincial level. The different sections of the Guadiana basin have different trade strategies. On the one hand, the Upper Guadiana basin is a net exporter, mainly of wine, barely importing any food commodity. On the other, the Lower Guadiana and TOP domain import low-value, high water-consuming cereals, while exporting high-value, low virtual-water content crops such as fruits. This reduces the demand on local (green and blue) water resources that can be used to provide ecological services and other more profitable uses.
Acknowledgements
We wish to thank all the people and institutions that have made this research possible. First, we would like to thank Alberto Garrido, Consuelo Varela, Paula Novo and Roberto Rodriguez. We would also like to thank Professor Arjen Hoekstra for his useful advices.
Finally, we can not forget the EU NeWater project and Marcelino Botin Foundation who sponsored this research.
Symbols
Glossary
Blue water – surface and ground water (Hoekstra and Chapagain, 2008).
Blue virtual-water content (Vb) – of a product is the volume of surface or ground water that evaporated as a result of the production of the product. In the case of crop production, the blue water content of a crop is defined as the evaporation of irrigation water from the field. In the cases of industrial production and domestic water supply, the blue water content of the product or service is equal to the part of the water withdrawn from ground or surface water (m3/ton) (Hoekstra and Chapagain, 2008).
Crop consumptive water use (CWU) – is defined as the accumulation of daily evapotranspiration over de complete growing period. It has two components: Green crop water and blue crop consumptive water use (m3/ha) (Hoekstra and Chapagain, 2008).
Crop water requirements (CWR) – is defined as the total water needed for evapotranspiration, from planting to harvest for a given crop in a specific climate regime, when adequate soil water is maintained by rainfall and/or irrigation so that it does not limit plant growth and crop yield (mm/time period) (Allen et al., 1998).
Crop water supply – is the quantity of irrigation water, in addition to rainfall, applied to meet a crop’s evapotranspiration need and normal crop production. It includes soil evaporation and some unavoidable losses under the given conditions. It is expressed in cubic meters for a crop period (m3/year).
Effective rainfall (Peff) – in irrigation practice, that portion of the total precipitation which is retained by the soil so that it is available for crop production (mm/time period) (FAO, 2008).
External water footprint (WFe) – is defined as the annual volume of water resources used in other countries or regions to produce goods and services consumed by the inhabitants of
the country or region concerned (km3/year, m3/capita/year) (Hoekstra and Chapagain, 2008).
Green virtual-water content (Vg) – of a product is the volume of rainwater that evaporated during the production process. This is mainly relevant for agricultural products, where it refers to the total rainwater evaporation from the field during the growing period of the crop (including both transpiration by the plants and other forms of evaporation) (m3/ton) (Hoekstra and Chapagain, 2008).
Green water – rainwater stored in the soil as soil moisture, also called soil water (Hoekstra and Chapagain, 2008).
Gross value added (GVA) – is the value of goods and services produced in an economy at different stages of the productive process (million €). The gross value added is equal to net output or benefit that can be used for the remuneration of productive factors.
Internal water footprint (WFi) – is defined as the use of domestic water resources to produce goods and services consumed by inhabitants of a country or region (km3/year, m3/capita/year) (Hoekstra and Chapagain, 2008).
Total economic agricultural production – is defined as the total economic value received by the agricultural sector of the region for the commodities sold in the market without taking subsidies into account (total €).
Virtual-water content (V) – the virtual-water content of a product (a commodity, good or service) is the volume of freshwater used to produce the product, measured at the place where the product was actually produced (production-site definition) (m3/ton) (Hoekstra and Chapagain, 2008).
Water footprint (WF) – the water footprint of an individual or community is defined as the total volume of freshwater that is used to produce the goods and services consumed by
the individual or community. A water footprint can be calculated for any well-defined group of consumers, including a family, business, village, city, province, state or nation. A water footprint is generally expressed in terms of the volume of water use per year (km3/year, m3/capita/year) (Hoekstra and Chapagain, 2008).
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Appendixes
